Surgical cutting instrument

ABSTRACT

A surgical instrument with a first cutting member having a passage therein and a second cutting member slidably received within the passage. A storage recess formed in said passage by the second cutting member has an inlet opening and a discharge opening with the first and second cutting members having a configuration that provides a cooperative shearing action between the members during relative movement of the members in a first direction with sheared material being deposited in the storage recess through the inlet. Means are provided to cause movement of the sheared material within the recess toward the discharge opening during relative movement of the members in a second direction with means also being provided to cause the relative movement of the cutting members in said first and second directions. A replaceable cutting tip for a surgical instrument with the replaceable tip having a cutting tip body of an elongated generally cylindrical configuration. The body includes a longitudinal bore, a forward end, a rearward end, and a knife edge defined by the forward end. Means are provided to engage cut material within the bore during movement of the tip body in a second direction to move the material in the direction of movement of the cutting tip body. During movement of the cutting tip body in a first direction, the cut material is disengaged and there is movement of the body with respect to cut material within the bore. Means may also be provided to position the cutting tip with its rearward end in engagement with a surgical instrument and with the means to engage and disengage cut material within the bore being fixed in a desired position with respect to the surgical instrument.

United States Patent [191 Niederer [4 1 Sept. 2, 1975 SURGICAL CUTTING INSTRUMENT [75] Inventor: Peter G. Niederer, Goleta, Calif.

[73] Assignee: Minnesota Mining and Manufacturing Company, St. Paul, Minn.

22 Filed: Mar. 4, 1974 21 Appl.No.:447,577

[52] US. Cl. 128/305 [51] Int. C1. A61B 17/32 [58] Field of Search 30/130, 228, 241, 242; 128/305, 310, 312, 318

[56] References Cited UNITED STATES PATENTS 1,167,014 1/1916 OBrien 128/305 1,867,624 7/1932 Hoffman 128/305 3,173,414 3/1965 Guillant 128/318 X 3,308,825 3/1967 Cruse.... 128/318 X 3,752,161 8/1973 Bent 128/312 3,800,783 4/1974 Jamshidi 128/310 3,815,604 6/1974 OMalley ct a1. 128/305 Primary ExaminerChanning L. Pace Attorney, Agent, or FirmAlexander, Sell, Steldt & DeLaI-Iunt w I .It .tiiliiitftu formed in said passage by the second cutting member has an inlet opening and a discharge opening with the first and second cutting members having a configuration that provides a cooperative shearing action between the members during relative movement of the members in a first direction with sheared material being deposited in the storage recess through the inlet. Means are provided to cause movement of the sheared material within the recess toward the discharge opening during relative movement of the members in a second direction with means also being provided to cause the relative movement of the cutting members in said first and second directions.

A replaceable cutting tip for a surgical instrument with the replaceable tip having a cutting tip body of an elongated generally cylindrical configuration. The body includes a longitudinal bore, a forward end, a rearward end, and a knife edge defined by the forward end. Means are provided to engage cut material within the bore during movement of the tip body in a second direction to move the material in the direction of movement of the cutting tip body. During movement of the cutting tip body in a first direction, the cut material is disengaged and there is movement of the body with respect to cut material within the bore. Means may also be provided to position the cutting tip with its rearward end in engagement with a surgical instrument and with the means to engage and disengage cut material within the bore being fixed in a desired position with respect to the surgical instrument.

13 Claims, 7 Drawing Figures PATENTED SEP- 2l975 SHEET 1 2 PATENTED 2|975 3,902,498

sum 2 or 2 SURGICAL CUTTING INSTRUMENT BACKGROUND OF THE INVENTION A family of surgical instruments have been developed to perform various gripping, holding, cutting, chipping or perforating operations on bone and tissue. The operation situs is frequently located in a relatively inaccessible place and, thus, the surgical instruments may have varying shapes to accommodate their usuage in a particular location. Further, to provide considerable force in performing a particular operation procedure, the surgical instrument may include a power source with control means to provide increased force during the operating procedure with delicate control of the surgical instrument. A surgical instrument with such a power source is described in the United States Patent to Bent, US. Pat. No. 3,752,161, dated Aug. 14, 1973, which is incorporated herein by reference.

In previous surgical instruments of the type generally referred to as forceps or rongeurs, cutting has generally been accomplished through movement of a cutting member against an anvil. During use of the instrument, the bone or tissue at the operation situs is heldbetween the cutting member and avil with the anvil and cutting member then undergoing relative movement to bring the sharpened edge of the cutting member into contact with the anvil. In this type of surgical instrument, the cutting member may become dulled from repeated contact with the anvil. This, in turn, may require replacement of the cutting member by disassembling the surgical instrument to replace the cutting member or to remove the cutting member for sharpening.

In the use of a surgical instrument for operations performed at a relatively inaccessible operation situs, the instrument may include a recess which receives cut material that is removed by the surgical procedure. Depending upon the extent of the operation and the amount of bone or tissue which is surgically removed, the cut material received in the recess may constitute a number of bites with each bite resulting from one cut ting movement of the instrument.

In an extensive operation, the number of bites may exceed the capacity of the recess for storage of surgically removed material. In this event, it may be necessary to withdraw the surgical instrument from the operation situs to discharge stored material from the recess before proceeding with the operation. If the operation is performed in an area where there is considerable bleeding, the time lost in withdrawing the surgical instrument from the operation situs may make the operation considerably more difficult. For example, when the surgical instrument is withdrawn from the operation situs, the flow of blood during the time required for removal of bites from the recess may make it necessary to remove blood from the operation situs before proceeding with the operation. 1

A further complication of withdrawing the surgical instrument from the operation situs is that time may be lost in cleaning the instrument before proceeding with the operation. At the beginning of the operation, the instrument will be in a clean' condition, e.g., by autoclaving. To clean the instrument, it is necessary to remove the bites of material from the rongeur under sterile conditions. This involves the expenditure of additional time which would lengthen the operation.

It is advantageous to both the surgeon and patient if a surgical operation can be performed in the shortest possible time. The shock of the operation on the patients system is related to the length of the operation since this determines the extent of anesthesia, the extent of supporting personnel to monitor the patients vital functions, and the time required in recovery before the regaining of consciousness. Also, if the operation is performed in a shorter period of time, difficulties in keeping the operation situs clear will be reduced.

In view of the aforementioned problems, it would be desirable to have a surgical instrument which would have less tendency to become dulled during repeated usage. Also, it would be desirable to have a surgical instrument in which dulling of the cutting member would not require disassembly of the instrument to replace the cutting member.

In addition, it would be desirable to have a surgical instrument with means for storing bites removed by the surgical procedure in which the surgical instrument would not have to be withdrawn from the operation situs during the operation to remove bites from the storage recess. This would permit more rapid performance of the operation with less time expended in keeping the surgical field clear, less shock to the pa tient, and less danger of infection.

SUMMARY OF THE INVENTION As a solution to the aforementioned problems, the present invention provides a surgical instrument having a first cutting member with a passage therein. A second cutting member is slidably received within the passage with a recess provided in the second cutting member. A storage recess formed by the recess in said second cutting member and said passage includes an inlet opening and a discharge opening with the first and second cutting members having a. configuration which provides cooperative shearing action between the cutting members during relative movement of the members in a first direction.

During relativemovement of the cutting members in the first direction, sheared material removed at the operation situs is deposited in the storage recess through the inlet opening. Means are also provided to cause movement of the sheared material within the recess toward the discharge opening during relative movement of the cutting members in a second direction. The relative movement of the cutting members in the first and second directions may result from a power source such as a motor as illustrated in the Bent patent or the relative movement of the cutting members may result from movement of gripping members which may be moved manually by the surgeon to transmit relative movement to the cutting members.

In the present surgical instrument, the discharge opening is spaced from the inlet opening to the storage recess. Thus, sheared material within the storage recess is ejected through the discharge opening at a point .which is displaced from the operation situs such that the discharge of sheared material does not interfere with the operation.

The cooperative shearing action between the first and second cutting members in the present surgical instrument reduces dulling of the cutting members so that the surgical instrument can be used for a longer time period before sharpening or replacement of the cutting members. Also, the cooperative shearing action between the first and second cutting members produces a cleaner cut so that less difficulty may be involved in removing bites of cut material from the operation situs.

During usage, the second cutting member may be slidably received within the passage within the first cutting member. Thus, the first cutting member serves to support the second cutting member and to maintain the second cutting member in a desired position for cooperation with the first cutting member. As bites of material are removed at the operation situs, the bites are deposited within a storage recess through an inlet opening, with movement of the first and second cutting members in a second direction causing movement of the bites toward a discharge opening that is displaced from the inlet opening. Sheared material which is ejected through the discharge opening is, thus, discharged at a point that is removed from the operation situs.

If the operation is minor, the capacity of the storage recess may be sufficient to retain the surgically removed bites without ejection of sheared material from the discharge opening. However, if the operation is more extensive and the number of bites exceeds the capacity of the recess, the bites may be ejected through the discharge opening without interference with the field of operation at the operation situs. Thus, the surgeon will not be required to withdraw the surgical instrument from the situs of the operation to remove bites from the storage recess. The surgeon will, therefore, be able to complete the operation in a shorter time which is a convenience to the surgeon and also reduces the shock to the patients system that would result from a longer operation.

In the present surgical cutting instrument, the recess in the second cutting member may include a smooth bottom slide surface which cooperates with a frictional surface within the passage. The frictional surface within the passage may be positioned to engage sheared material supported on the smooth surface and to move the sheared material along the smooth surface during relative movement of the first and second cutting members in said second direction.

The frictional surface provided within the passage is a serrated surface directionally biased to engage sheared material within the recess during relative movement of the cutting members in the second direction and to disengage the sheared material within the recess during relative movement of the cutting members in the first direction. In this manner, the sheared material may be moved in a stepwise manner along the smooth bottom surface from the inlet opening to the discharge opening through engagement of the directionally biased frictional surface with the material during each relative movement of the cutting members in the second direction.

In the present surgical instrument, the first cutting member may be movable while the second cutting member is fixed. The first cutting member may have a generally elongated construction, an outer end defining a knife edge, and the passage in the first cutting member positioned in a generally axial direction with respect to the first cutting member. The second cutting member may have a generally elongated construction with an outer support surface conforming to the surface of the passage to slidably support the first cutting member while the second cutting member may include an outer end defining an inwardly facing gripping surface and a peripheral shearing surface which conforms with the shape of the knife edge. Bone or tissue may, thus, be gripped between the gripping surface and the knife edge with the gripped material then being sheared through movement of the first cutting member relative to the second cutting member to bring the knife edge and peripheral shearing surface into close shearing proximity.

In addition to providing an improved surgical instrument, as described above, the present invention also provides a replaceable cutting tip which may be used with a surgical instrument. Through use of the replaceable cutting tip, the surgical instrument may be more easily maintained without having to disassemble the instrument to replace or sharpen its cutting members.

The replaceable cutting tip may include a cutting tip body having an elongated generally cylindrical configuration with a longitudinal bore defined within the body. The cutting tip body includes a forward end and a rearward end with the forward end defining a knife edge. Additionally, means may be provided to engage sheared material within the bore of the replaceable cutting tip during movement of the cutting tip body in a second direction and to disengage sheared material within the bore during movement of the cutting tip body in a first direction. Means may also be provided to position the replaceable cutting tip with its rearward end in engagement with a surgical instrument and with the means to engage and disengage cut or sheared material within the bore of the cutting tip being fixed in a desired position with respect to the surgical instrument.

The means to engage and disengage sheared material within the bore of the cutting tip body may include a serrated frictional surface with the frictional surface being directionally biased to exert an engaging force on sheared material within the bore of the cutting tip on movement of the cutting tip body in said second direction.

Preferably, the replaceable cutting tip includes a wall having a generally conical exterior surface and with the wall being progressively reduced in thickness in proceeding toward the knife edge at the forward end of the cutting tip. The wall may, thus, act as a wedge in exerting transverse force on material which has been cut by contact with the knife edge, with the cut being progressively enlarged through contact with the exterior surface of the cutting tip.

BRIEF DESCRIPTION OF THE DRAWINGS To further illustrate the invention, reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention, and in which:

FIG. 1 is a side elevational view, partially in section, of a surgical cutting instrument with bone or tissue extending into a gap between first and second cutting members which undergo relative movement in shearing bites of material from the bone or tissue;

FIG. 1A is a sectional view taken along line lA-lA of FIG. I which illustrates the second cutting member slidably received within a passage in the first cutting member with a storage recess for receipt of bites of sheared material which are conveyed to a discharge opening that is removed from the operation situs;

FIG. 2 is an enlarged vertical cross-sectional view of the instrument of FIG. 1 in which the first and second cutting members have undergone relative movement in a first direction to remove a bite of bone or tissue with the bite being deposited into the storage recess FIG. 3 is a sectional view taken along line 3-3 of FIG. 2 demonstrating the manner in which the outer surface of the second cutting member engages a passage within the first cutting member to slidably support the first cutting member while permitting relative movement between the first and second cutting members;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 2 illustrating the manner of supporting the first cutting member through contact between the passage in the first cutting member with the exterior surface of the second cutting member;

FIG. 5 is an enlarged vertical cross-sectional view of the forward end of the surgical instrument in which serrated frictional surfaces are provided within a bore in a replaceable cutting tip and within the passage in the first cutting member, which surfaces are directionally biased to exert an engaging force on sheared material in the storage recess during relative movement of the cutting members to move the sheared material in the direction of a discharge opening from the recess, and

FIG. 5A is a perspective view illustrating a means for fixing the position of the replaceable cutting tip shown in FIG. 5 with respect to a surgical instrument.

DETAILED DESCRIPTION A surgical cutting instrument 2, as illustrated in FIG. I, may include a first cutting member 4 having a generally elongated configuration with a longitudinal passage 6 within the first cutting member. A second cutting member 8 having an exterior surface 9 is positioned within the passage 6 with the exterior surface 9 contacting the surface of the passage to provide slidable support for the first cutting member 4.

A storage recess 10 is defined in the passage 6 by second cutting member 8 with the recess having an inlet opening 12 and a discharge opening 14. A replaceable cutting tip 16 may be positioned on the first cutting member 4 with the replaceable tip defining a knife edge 18 at its forward end. The second cutting member 8 may include a transversely positioned gripping shoe 20 positioned at its forward end with the gripping shoe including a lateral or peripheral edge surface 22 and a transversely positioned gripping surface 23.

As illustrated in FIG. 1, tissue or bone 24 which is to be removed at the operation situs. may be positioned between the knife edge 18 and the transversely positioned gripping surface 23. Thus, during relative movement of the first and second cutting members 4 and 8 in a manner to be described, a shearing force may be exerted on the material 24 through the cooperative action of the shoe 20 and the knife edge 18.

A fluid motor designated 26 may be used in providing relative movement of the first and second cutting members 4 and 8. The fluid motor 26 may, for example, take the form of the fluid motor described in US. Pat. No. 3,752,161 to increase the cutting or breaking force which is applied in a surgical operation while retaining delicate control by the surgeon. However, the present surgical instrument 2 may be actuated in any suitable manner or by hand and, thus, the reference to fluid motor 26 is merely to illustrate one means of actuating the surgical instrument.

The fluid motor 26 may include a trigger 28 and a grip 29 with actuation of the trigger controlling the movement of a piston 30 within a cylinder 32 to transmit movement to the first cutting member 4. Thepiston 30 is shown in FIG. 1 in a retracted position under the influence of a biasing spring 34.

A support hub 36 is positioned about the exterior surface of the first cutting member 4 with the support hub being fixedly held by a collar 38 in threaded engagement with a body 39 for hydraulic motor 26. One end of the biasing spring 34 is retained within a recess 40 formed in the hub 36 with the recess terminating at a ledge 42 which engages the spring. The other end of the spring 34 engages the piston 30 such that the biasing force of the spring tends to move the piston to the right from its position shown in FIG. I.

The second cutting member 8 may be supported with respect to the hub 36 by any suitable means such as screws 44 and 45. As will be described, the construction of the surgical instrument 2 permits the support of the first cutting member 4 by the second cutting member 8 while permitting relative movement between the two cutting members.

Turning to FIG. 1A, which is a sectional view taken along line lA-IA of FIG. 1, the passage 6 Within first cutting member 4 surrounds the second cutting member 8 whose outer surface 9 is in contact with the surface of the passage. The recess 10 within passage 6 formed by the second cutting member 8 leads to the laterally directed discharge opening 14. Thus, sheared material within the recess 10 may be transmitted to the discharge opening 14 where it is ejected at a point that is removed from the operation situs.

FIG. 2 is an enlarged vertical cross-sectional view of the cutting members 4 and 8 after relative movement of the cutting members in a first direction to shear off a bite 46 from bone or tissue 24 at the situs of the operation. To facilitate the cutting action, the replaceable cutting tip 16 may include a conical outer surface 47 which tapers inwardly toward the knife edge 18. This provides the replaceable cutting tip 16 with a wall 49 whose thickness is progressively increased in thickness in a direction away from the knife edge 18. In cutting a bite 46 from the bone or tissue material 24, the material may be cut initially through contact with knife edge 18 with the cut then being progressively opened through a wedging action by contact of the material 24 with the conical surface 47. The wedging action produced by the conical surface 47 provides a transverse breaking force to the material 24 which assists the severing of hard material such as bone or bony tissue.

Preferably, the knife edge 18 is of a circular shape with the lateral edge surface 22 of the gripping shoe 20 having a corresponding circular shape. With knife edge 18 having a circular shape, cutting is provided at any point around the knife edge that is brought into shearing proximity with the lateral edge surface 22. Thus, it is not necessary that the knife edge 18 be aligned in any particular manner with the material 24 to be cut as would be the case if the knife edge had a shape where the cutting effect of the knife edge would be altered depending upon its position with respect to the material being cut.

As shown in FIG. 2, the knife edge 18 and lateral edge surface 22 are brought into close shearing proximity during cutting of a bite 46 from the material 24. When in close shearing proximity, the knife edge 18 slides over the lateral edge surface 22. This provides a cooperative shearing action between the knife edge 18 and lateral edge surface 22 in which the knife edge is not forced against a rigidly positioned anvil surface which would produce more rapid dulling of the knife edge. The movement of the knife edge I8 and the lateral edge surface 22 in cutting the bite 46 also provides shearing coaction between the knife edge and lateral edge surface which cuts more effectively than the action provided by movement of a knife edge surface against a rigid anvil.

Additionally, the sliding movement of the knife edge 18 over the lateral edge surface 22, shown in FIG. 2, forces the bite 46 into the recess 10. As the bite 46 is moved into the recess 10, a serrated directionally bi ased frictional surface 51 therein engages the bite on movement of the first cutting member 4 in the direction of discharge opening 14. This moves the bite 46 along a smooth slide surface 48 toward the discharge opening 14.

As shown, the discharge opening 14 is displaced from inlet 12 (see FIG. 1). Thus, when sheared material is ejected from the recess through the discharge opening I4, its point of ejection is removed from the operation situs. The ejection of sheared material through the discharge opening 14 does not, therefore, interfere with the operation. This is of considerable importance since it permits the performance of the operation in a shorter time period which is of advantage to the surgeon and is also of considerable advantage to the patient.

During relative movement of the cutting members 4 and 8 with the knife edge 18 and the lateral edge surface 22 being moved apart, the bites 46 are transported through contact with a frictional surface 51 along the slide surface 48 toward the discharge 14. Upon reaching the discharge 14, the bites 46 engage an ejection surface 50. The ejection surface 50 is angled to provide a transverse ejecting force to bites 46 as they contact the ejection surface. The bites 46 are, thus, ejected through the discharge opening 14. The rearward end of the replaceable cutting tip 16 may, as indicated, be connected to the first cutting member through a threaded connection 52.

Moving to the right in FIG. 2, the passage 6 within first cutting member 4 leads to an enlarged passage 54 while the outer surface 9 of second cutting member 8 leads to an enlarged surface 56 positioned slidably within the enlarged passage. As will be described, the second cutting member 8 may be fixedly held with the first cutting member 4 being moved relative to the second cutting member. During movement of the first cut ting member 4, the first cutting member may be slid ably supported through contact of the passage 6 with surface 9 and contact of the enlarged passage 54 with enlarged surface 56.

Movement of the first cutting member 4 is illustrated by arrow A in which knife edge 18 undergoes movement toward the lateral edge surface 22 to sever a bite 46 from the bone or tissue 24. During movement of first cutting member 4 in the direction of the arrow A, a drive end 58 formed integrally with the first cutting member is moved to its solid line position by a force which overcomes the biasing force of spring 34. Such movement may, for example, be provided by movement of a piston, such as piston 30 illustrated in FIG. 1. On removing the driving force from drive end 58, the action of biasing spring 34 then returns the drive end to its phantom line position 58'. During this movement, the drive end 58 and the first cutting member 4 un dergo movement in a direction opposite to that indicated by arrow A, and the knife edge 18 is moved away from the lateral edge surface 22.

As stated, the second cutting member 8 may be held in a fixed position by screws 44 and 45 with the outer surfaces 9 and 56 of the second cutting member slidably supporting the first cutting member 4. The screws 44 and 45 threadedly engage apertures 60 and 62 in the second cutting member 8 with the screw fixedly held by the hub 36 which has a flange 64 that is engaged by the collar 38 (see FIG. 1). Screw 44 extends through a side opening 66 in the hub 36 while screw 45 extends through a side opening 68. The head of the screw 45 may be retained within a recess 70 such that the head does not interfere with positioning of the collar 38 about the hub 36.

A saddle-shaped recess 72 is provided within the body of first cutting member 4 and a saddle-shaped support spacer 74 is positioned within the recess. The saddle-shaped support spacer 74 has the same configuration as recess 72; however, the spacer has a length which is less than that of the recess. This permits relative movement between spacer 74 and the first cutting member 4 with the degree of relative movement determined by the distance between the ends of recess 72 and the ends of the spacer.

The screws 44 and 45, in addition to passing through apertures 66 and 68 of hub 36, also pass through apertures 78 and 80 of the spacer 74. This fixes the position of the spacer 74. The spacer 74 terminates at a pair of upper surfaces 76 shown in phantom line drawing which are in contact with corresponding surfaces on the first cutting member 4.

FIG. 3, which is a sectional view taken along line 33 of FIG. 2, illustrates the manner in which the first cutting member 4 is slidably supported by the second cutting member 8. As illustrated, the position of second cutting member 8 may be fixed with a plurality of screws, such as screw 44 which threadably engages aperture 60 in the second cutting member 8. The saddleshaped support spacer 74 is also fixedly positioned with respect to hub 36 while the first cutting member 4 is slidably supported through contact with second cutting member 8 and the support spacer 74. Relative movement is, thus, permitted with the first cutting member 4 being free to slide in a longitudinal direction within the limits permitted by the length of the recess 72 with respect to the length of the support spacer 74.

FIG. 4, which is a sectional view along line 4-4 of FIG. 2, illustrates further the manner in which first cutting member 4 is slidably supported by the second cutting member 8. As illustrated, the first cutting member 4 has been moved forwardly to bring an end surface 82 or recess 72 into close proximity with one end 84 of the spacer 74. At the same time, the other end 86 of recess 72 is moved away from the spacer 74. The knife edge 18 is, thus, advanced toward the gripping shoe 20 while first cutting member 4 is slidably supported by the second cutting member 8. This movement is designated by arrow A which is the same designation used in FIG. 2 to illustrate this movement of the first cutting member 4.

After completion of the cutting operation, the first cutting member 4 is moved in the direction of arrow B. During this movement, the surface 82 of recess 72 is moved away from the end 84 of spacer 74. During this movement, the surface 86 may be moved through the distance designated C to bring the surface 86 into close proximity with an end 88 of spacer 74,

FIG. is an enlarged vertical sectional view, similar to FIG. 2, illustrating the first cutting member 4 and second cutting member 8 with a plurality of bites 46 supported on slide surface 48. During movement of the knife edge 18 toward gripping shoe 20, the frictionally biased surface 51 disengages the bites 46 within the storage recess 10. However, after severing a new bite 46 and depositing it in recess 10, the frictionally biased surface 51 engages the bites 46 to move the bites toward the discharge opening 14 as the knife edge 18 is moved away from shoe 20.

If desired, the passage 6 in first cutting member 4 may also include a frictionally biased surface 90 positioned in aligned relation with frictional surface 51. Thus, during movement of the first cutting member 4, both the surfaces 51 and 90 function'to engage bites 46 on movement of the first cutting member in one direction and to disengage the bites on movement of the first cutting member in a second direction.

In the use of two frictional surfaces 51 and 90, it is desirable that the replaceable cutting tip 16 be precisely positioned on the first cutting member 4 so that the two frictional surfaces are properly aligned. To accomplish this result, a connection 92 between cutting tip 16 and first cutting member 4 may be employed which fixes the rotational position of the cutting tip with respect to the first cutting member.

A suitable connection for fixing the rotational position of cutting tip 16 with respect to first cutting member 4 is illustrated in FIG. 5A. The cutting tip 16 may include a male socket member 94 which fits in a corresponding female socket member in the first cutting member 4. A shoulder 95 on the tip 16 then engages an end surface 97 on the first cutting member 4 with a pin 96 on the tip in engagement with an L-shaped slot 98 in the first cutting member. After inserting the pin 96 into slot 98, the replaceable cutting tip 16 may be rotated with respect to the first cutting member 4 to bring the pin into contact with a slot end surface 100. This, then, fixes the rotational position of the replaceable cutting tip 16 with respect to the first cutting member 4 which, in turn, aligns the frictionally biased surfaces 51 and 90 (FIG. 5) within the cutting tip and the first cutting member.

I claim:

1. A surgical cutting instrument comprising:

a first cutting member having a passage therein;

a second cutting member slidably received within said passage;

a recess in said second cutting member;

said passage having an inlet opening and a discharge opening;

means to cause relative movement of said members in first and second directions;

said first and second cutting members having a configuration for cooperative shearing action upon bone or tissue located between said members at an operation situs during relative movement of said members in a first direction, said cooperative shearing action causing sheared bone or tissue material to be deposited in said recess and into said passage through said inlet opening;

means to cause movement of said sheared bone or tissue material within said recess and passage toward said discharge opening during relative ,movement of said members in a second direction;

and

said discharge opening being spaced from said inlet opening such that said sheared bone or tissue material ejected through said discharge opening is displaced from the operation situs.

2. A surgical tool according to claim 1 wherein the means to cause movement ofsaid sheared bone or tissue material within said-passage toward said discharge opening during relative movement of said first and second cutting members in a second direction comprises a smooth slide surface in said recess and a frictional surface within said passage, said frictional surface and said smooth slide surface cooperating to engage sheared bone or tissue material therebetween to thereby move said sheared bone or tissue material in said recess and passage toward said discharge opening during relative movement of said first and second cutting members in said second direction.

3. The surgical tool of claim 2 wherein said frictional surface comprises a serrated surface directionally biased to engage sheared material during relative movement of said cutting members in said second direction and to disengage the sheared material during relative movement of said cutting members in said first direction.

4. The surgical tool of claim 1 wherein said first cutting member is movable and said second cutting member is fixed;

said first cutting member having a generally clongated configuration, an outer end, a knife edge on said outer end, with said passage positioned generally axially of said first cutting member;

said second cutting member having a generally elongated configuration and an outer support surface conforming to the surface of said passage and slidably engaging said passage in supporting relationship with said first cutting member;

said second cutting member having an outer end which defines a gripping surface and a shearing surface;

said shearing surface having a shape which conforms with the shape of said knife edge,

whereby bone or tissue material to be sheared may initially be gripped between said gripping surface and said knife edge with said bone or tissue material then being sheared by movement of the first cutting member relative to the second cutting member to bring the knife edge and shearing surface into close shearing proximity.

5. The surgical tool of claim 4 wherein the outer end of said first cutting member comprises a cutting tip releasably secured thereto;

said cutting tip having a passage aligned with said passage in said first cutting member, and

said cutting tip having an outer end which defines said knife edge,

whereby said cutting tip may be replaced when said knife edge becomes dulled.

6. The cutting tool of claim 5 including a frictional surface within said passage in said cutting tip, and

means to align said frictional surface in the passage of said cutting tip with said frictional surface in the passage in said first cutting member.

7. The surgical cutting tool of claim 1 including power operated means to cause relative movement of said first and second cutting members.

8. A replaceable cutting tip for a surgical to'ol comprising a cutting tip body having an elongated configuration;

a longitudinal bore in said body;

said body having a forward end and a rearward end;

said forward end defining a knife edge;

means within said bore adapted to engage and disengage material therewithin on movement of said body in a second direction and first direction, respectively, and

means to releasably secure said cutting tip with said rearward end in engagement with a surgical instrument.

9. The replaceable cutting tip of claim 8 wherein said means adapted to engage and disengage material within said bore is a frictional surface, and

said frictional surface is a serrated surface directionally biased to exert a frictional force on material within said bore on movement of said cutting tip body in said second direction.

10. The replaceable cutting tip of claim 8 including a wall on said body;

a generally conical forward exterior surface on said body, and

said wall being progressively reduced in thickness in the direction of said knife edge,

whereby said wall and forward exterior surface act as a wedge in exerting a breaking force on material being cut'by contact with said knife edge with the cut being progressively enlarged through contact with said forward exterior surface.

11. The replaceable cutting tip of claim 8 including means to uniformly fix the rotational position of said body with respect to a surgical instrument in engagement with the rearward end of said cutting tip.

12. The replaceable cutting tip of claim 9 including means to uniformly fix the location of said frictional surface with respect to a surgical instrument in engagement with the rearward end of said cutting tip.

13. The replaceable cutting tip of claim 8 wherein said knife edge is circular. 

1. A surgical cutting instrument comprising: a first cutting member having a passage therein; a second cutting member slidably received within said passage; a recess in said second cutting member; said passage having an inlet opening and a discharge opening; means to cause relative movement of said members in first and second directions; said first and second cutting members having a configuration for cooperative shearing action upon bone or tissue located between said members at an operation situs during relative movement of said members in a first direction, said cooperative shearing action causing sheared bone or tissue material to be deposited in said recess and into said passage through said inlet opening; means to cause movement of said sheared bone or tissue material within said recess and passage toward said discharge opening during relative movement of said members in a second direction; and said discharge opening being spaced from said inlet opening such that said sheared bone or tissue material ejected through said discharge opening is displaced from the operation situs.
 2. A surgical tool according to claim 1 wherein the means to cause movement of said sheared bone or tissue material within said passage toward said discharge opening during relative movement of said first and second cutting members in a second direction comprises a smooth slide surface in said recess and a frictional surface within said passage, said frictional surface and said smooth slide surface cooperating to engage sheared bone or tissue material therebetween to thereby move said sheared bone or tissue material in said recess and passage toward said discharge opening during relative movement of said first and second cutting members in said second direction.
 3. The surgical tool of claim 2 wherein said frictional surface comprises a serrated surface directionally biased to engage sheared material during relative movement of said cutting members in said second direction and to disengage the sheared material during relative movement of said cutting members in said first direction.
 4. The surgical tool of claim 1 wherein said first cutting member is movable and said second cutting member is fixed; said first cutting member having a generally elongated configuration, an outer end, a knife edge on said outer end, with said passage positioned generally axially of said first cutting member; said second cutting member having a generally elongated configuration and an outer support surface conforming to the surface of said passage and slidably engaging said passage in supporting relationship with said first cutting member; said second cutting member having an outer end which defines a gripping surface and a shearing surface; said shearing surface having a shape which conforms with the shape of said knife edge, whereby bone or tissue material to be sheared may initially be gripped between said gripping surface and said knife edge with said bone or tissue material then being sheared by movement of the first cutting member relative to the second cutting member to bring the knife edge and shearing surface into close shearing proximity.
 5. The surgical tool of claim 4 wherein the outer end of said first cutting member comprises a cutting tip releasably secured thereto; said cutting tip having a passage aligned with said passage in said first cutting member, and said cutting tip having an outer end which defines said knife edge, whereby said cutting tip may be replaced when said knife edge becomes dulled.
 6. The cutting tool of claim 5 including a frictional surface within said passage in said cutting tip, and means to align sAid frictional surface in the passage of said cutting tip with said frictional surface in the passage in said first cutting member.
 7. The surgical cutting tool of claim 1 including power operated means to cause relative movement of said first and second cutting members.
 8. A replaceable cutting tip for a surgical tool comprising a cutting tip body having an elongated configuration; a longitudinal bore in said body; said body having a forward end and a rearward end; said forward end defining a knife edge; means within said bore adapted to engage and disengage material therewithin on movement of said body in a second direction and first direction, respectively, and means to releasably secure said cutting tip with said rearward end in engagement with a surgical instrument.
 9. The replaceable cutting tip of claim 8 wherein said means adapted to engage and disengage material within said bore is a frictional surface, and said frictional surface is a serrated surface directionally biased to exert a frictional force on material within said bore on movement of said cutting tip body in said second direction.
 10. The replaceable cutting tip of claim 8 including a wall on said body; a generally conical forward exterior surface on said body, and said wall being progressively reduced in thickness in the direction of said knife edge, whereby said wall and forward exterior surface act as a wedge in exerting a breaking force on material being cut by contact with said knife edge with the cut being progressively enlarged through contact with said forward exterior surface.
 11. The replaceable cutting tip of claim 8 including means to uniformly fix the rotational position of said body with respect to a surgical instrument in engagement with the rearward end of said cutting tip.
 12. The replaceable cutting tip of claim 9 including means to uniformly fix the location of said frictional surface with respect to a surgical instrument in engagement with the rearward end of said cutting tip.
 13. The replaceable cutting tip of claim 8 wherein said knife edge is circular. 